Very slow speed with Atheros QCA9377 on Debian10

[transysthor]

I have recently installed Debian 10 stable but now my WiFi speed is very slow, the speed dropped from ~400Mbs to ~40Mbps.
HW: Asus F556U, i7 7500U, Qualcomm Atheros QCA9377 802.11ac connected trough Asus RT-AC3200 wireless router on 5Ghz.

Code: Select all

03:00.0 Network controller: Qualcomm Atheros QCA9377 802.11ac Wireless Network Adapter (rev 31)
	Subsystem: AzureWave QCA9377 802.11ac Wireless Network Adapter
	Flags: bus master, fast devsel, latency 0, IRQ 131, IOMMU group 13
	Memory at ef200000 (64-bit, non-prefetchable) [size=2M]
	Capabilities: [40] Power Management version 3
	Capabilities: [50] MSI: Enable+ Count=1/8 Maskable+ 64bit-
	Capabilities: [70] Express Endpoint, MSI 00
	Capabilities: [100] Advanced Error Reporting
	Capabilities: [148] Virtual Channel
	Capabilities: [168] Device Serial Number 00-00-00-00-00-00-00-00
	Capabilities: [178] Latency Tolerance Reporting
	Capabilities: [180] L1 PM Substates
	Kernel driver in use: ath10k_pci
	Kernel modules: ath10k_pci

I installed the firmware-atheros but I get some errors in dmesg :

Code: Select all

[   11.387284] ath10k_pci 0000:03:00.0: enabling device (0000 -> 0002)
[   11.391017] ath10k_pci 0000:03:00.0: pci irq msi oper_irq_mode 2 irq_mode 0 reset_mode 0
[   11.694073] ath10k_pci 0000:03:00.0: firmware: failed to load ath10k/pre-cal-pci-0000:03:00.0.bin (-2)
[   11.700335] ath10k_pci 0000:03:00.0: firmware: failed to load ath10k/cal-pci-0000:03:00.0.bin (-2)
[   11.750551] ath10k_pci 0000:03:00.0: firmware: direct-loading firmware ath10k/QCA9377/hw1.0/firmware-6.bin
[   11.753738] ath10k_pci 0000:03:00.0: qca9377 hw1.1 target 0x05020001 chip_id 0x003821ff sub 1a3b:2b31
[   11.757029] ath10k_pci 0000:03:00.0: kconfig debug 0 debugfs 0 tracing 0 dfs 0 testmode 0
[   11.762028] ath10k_pci 0000:03:00.0: firmware ver WLAN.TF.2.1-00021-QCARMSWP-1 api 6 features wowlan,ignore-otp crc32 42e41877
[   11.848485] ath10k_pci 0000:03:00.0: firmware: direct-loading firmware ath10k/QCA9377/hw1.0/board-2.bin
[   11.855377] ath10k_pci 0000:03:00.0: board_file api 2 bmi_id N/A crc32 8aedfa4a
[   12.037753] ath10k_pci 0000:03:00.0: htt-ver 3.56 wmi-op 4 htt-op 3 cal otp max-sta 32 raw 0 hwcrypto 1
[   12.159225] ath10k_pci 0000:03:00.0 wlp3s0: renamed from wlan0

It seems that are 2 calibration bin files that are not loaded.
In the past I was using Ubuntu 18.04LTS and I didn't had this problem, in fact when I did the ubuntu 20 update I had encountered the same low speed problem, so I returned to 18.04.
But I would like to keep using Debian for a couple of reasons and this issue is bothering me. Now I am on Debian Bullseye (5.9.0-1-amd64) since I was thinking that is something kernel related, but no luck.
It is very strange since even with the ubuntu 18 live usb I can get ~400 Mbit on speedtest. When I boot the Ubuntu 18 live usb and check for dmesg it doesn't show those failures of loading the calibration files/modules.
I copied the files /lib/firmware/ath10k/QCA9377 from ubuntu18 to Debian10 but no luck.
What can be done ?

[Head_on_a_Stick]

when I did the ubuntu 20 update I had encountered the same low speed problem

Could be a kernel regression then.

What can be done ?

https://wiki.debian.org/DebianKernel/GitBisect

[transysthor]

If I understood well, this tool will verify all the new kernels after the good one (between the range in my case 5.3.0-28-generic which is the ubuntu 18.04 kernel and the Debian10 kernel) and after that it will copy some configuration to the new one, than it will compile the new custom kernel and use it as the default/primary kernel.
I think there will be multiple chances of breaking the actual installed version of Debian, can it be undone easily by reverting to a previous kernel or should I expect to a new installation of Debian?
This will be my first time doing this kind of kernel stuff.
Thanks!

[Head_on_a_Stick]

can it be undone easily by reverting to a previous kernel

Yes, just reinstall the original version.

[jaimet]

Rolling back to a previous firmware version (which is reasonably easy to do) may help:
https://www.reddit.com/r/linuxmint/comm ... ghz_issue/

Edit: Please also see my other post re this card.